Every summer, lakes of meltwater form on the ice surface. When the weight of the water becomes too great, the ice splits open to form channels that can drain the lakes in a matter of hours. These supraglacial lake drainage events transport heat to the base of the ice sheet and lubricate the bedrock. It is hypothesized that this causes the ice sheet to accelerate its march to the ocean. (Photo by Ian Joughin, University of Washington Polar Science Center)[back]
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